Manganese Mobilization and Enrichment during Soil Aquifer Treatment (SAT) of Effluents, the Dan Region Sewage Reclamation Project (Shafdan), Israel

Abstract

The composition of groundwater reclaimed from tertiary soil aquifer treatment systems reflects the dynamic processes taking place in the subsurface, between the infiltration basin and the production wells. At the end of year 2000, following more than a decade of operation, high Mn concentrations (2 micromol L(-1) < or = Mn < or = 40 micromol L(-1)) appeared in the reclaimed effluents of the Dan Region Sewage Reclamation Project (Shafdan), Israel. A mass balance indicates that the high Mn excess originated from the aquifer rocks, most likely following reduction of sedimentary Mn-oxides under suboxic conditions. The subsequent adsorption of the Mn2+ results in a slow Mn2+ front that advances in the direction of groundwater flow only when all the Mn2+ exchangeable sites are saturated. A retardation factor obtained from two independent estimates based on a simple reduction-adsorption-advection model yields a value of about 10. This explains the delayed appearance of the high Mn concentrations at a distance of only -500 m from the infiltration basin.

Mobilization and retardation of reduced manganese in sandy aquifers: Column experiments, modeling and implications

“…(10)) to be ca. 10 (Oren et al, 2007). This is lower by almost an order of magnitude than the retardation factor of 65-94 obtained in the experimental columns (Fig 6).…”

“…High Mn 2+ concentrations appeared in the recovery wells in the year 2000, about 12 years after the onset of the SAT operation ( Fig. 7; Oren et al, 2007). The Mn retardation factor within the Shafdan aquifer was estimated from the water to Mn velocity ratio (Eq.…”

“…High concentrations of Mn 2+ are common in anthropogenically disturbed aquatic environments such as acid mine drainage, landfill leachate, soil aquifer treatment (SAT) of effluents, and river-bank filtration systems (Fllipek et al, 1987;Von Gunten et al, 1991;Thomas et al, 1994;Ludvigsen et al, 1998;Woo and Choi, 2001;Scott et al, 2002;Oren et al, 2007;Buschmann et al, 2007). Such environments may serve as "natural" laboratories for the study of Mn mobilization and re-deposition in the sedimentary record under variable environmental conditions.…”

“…Such environments may serve as "natural" laboratories for the study of Mn mobilization and re-deposition in the sedimentary record under variable environmental conditions. Mobilization of manganese in aquifers due to recharge of organic-rich water and microbial activity has been the focus of several field and laboratory studies (Jacobs et al, 1988;Von Gunten et al, 1991;Matsunaga et al, 1993;Bertin, 1993, 1994;Thomas et al, 1994;Ludvigsen et al, 1998;Petrunice et al, 2005, Oren et al, 2007. Precipitation of Mn-oxides due to oxidation of Mn 2+ by dissolved oxygen was suggested in several studies as the process responsible for the down flow decrease of dissolved Mn 2+ in aquifers (Bourg and Bertin, 1994;Klinchuch and Delfino, 2000;Scott et al, 2002).…”

“…Thomas et al, 1994;Petrunice et al, 2005;Oren et al, 2007) and in packed column experiments (Petrunice et al, 2005). Adsorption of Mn 2+ was also described as an intermediate process, followed by particle surface oxidation of Mn 2+ and precipitation of solid Mn-oxides, for Mn retardation in an alluvial aquifer (Bourg and Bertin, 1993).…”